The SG-30x90-4 Scientific Grade Honeycomb Core Optical Breadboard has a 30 in. width, a 90 in. length, and is 4.3 inches thick with 1/4-20 holes on a 1 inch grid. The SG Series provides rock-solid stability and rigidity to support demanding research applications. It demonstrates an outstanding <±0.004 in. flatness over two square feet. The SG Breadboard offers a 3/16 in. ferromagnetic steel surface, enhanced damping, sealed holes, and a steel honeycomb core. This means the SG Series still out-performs other manufacturers’ top-of-the-line breadboards.